Anaesthesia Queen Elizabeth Hospital King's Lynn NHS Foundation Hospital, Kings Lynn, UK.
Anaesthesia and Critical Care, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, UK.
Br J Anaesth. 2021 Apr;126(4):889-895. doi: 10.1016/j.bja.2020.12.031. Epub 2021 Feb 3.
Studies of pulmonary denitrogenation (pre-oxygenation) in obstetric populations have shown high flow nasal oxygen therapy (HFNO) is inferior to facemask techniques. HFNO achieves median end-tidal oxygen fraction (FE'O) of 0.87 after 3 min. As HFNO prolongs safe apnoea times through apnoeic oxygenation, we postulated that HFNO would still extend safe apnoeic times despite the lower FE'O after pre-oxygenation.
The Interdisciplinary Collaboration in Systems Medicine simulation suite, a highly integrated, high-fidelity model of the human respiratory and cardiovascular systems, was used to study the effect of varying FE'O (60%, 70%, 80%, and 90%) on the duration of safe apnoea times using HFNO and facemask techniques (with the airway open and obstructed). The study population consisted of validated models of pregnant women in active labour and not in labour with BMI of 24, 35, 40, 45, and 50 kg m.
HFNO provided longer safe apnoeic times in all models, with all FE'O values. Labour and increased BMI reduced this effect, in particular a BMI of 50 kg m reduced the improvement in apnoea time to 1.8-8.5 min (depending on the FE'O), compared with an improvement of more than 60 min in the subject with BMI 24 kg m.
Despite generating lower FE'O, HFNO provides longer safe apnoea times in pregnant subjects in labour. Care should be taken when used in patients with BMI ≥50 kg m as the extension of the safe apnoea time is limited.
针对产科人群的肺去氮（预充氧）研究表明，高流量鼻氧疗法（HFNO）不如面罩技术。HFNO 在 3 分钟后可达到中位呼气末氧分数（FE'O）0.87。由于 HFNO 通过无呼吸给氧延长了安全无呼吸时间，我们推测，尽管预充氧后的 FE'O 较低，但 HFNO 仍会延长安全无呼吸时间。
采用跨学科协同系统医学模拟套件，这是一个高度集成、高保真的人体呼吸和心血管系统模型，用于研究不同 FE'O（60%、70%、80%和 90%）对 HFNO 和面罩技术（气道开放和阻塞）下安全无呼吸时间的影响。研究人群包括处于活跃分娩和非分娩状态、BMI 为 24、35、40、45 和 50 kg/m 的孕妇的验证模型。
HFNO 在所有模型中均提供了更长的安全无呼吸时间，所有 FE'O 值均如此。分娩和 BMI 的增加削弱了这种效果，特别是 BMI 为 50 kg/m 时，与 BMI 为 24 kg/m 的患者的改善超过 60 分钟相比，无呼吸时间的改善降低到 1.8-8.5 分钟（取决于 FE'O）。
尽管 HFNO 产生的 FE'O 较低，但在分娩的孕妇中仍能提供更长的安全无呼吸时间。在 BMI≥50 kg/m 的患者中使用时应谨慎，因为安全无呼吸时间的延长是有限的。
